I am new to this site and have an E-PL1 with my E-PL5 on pre-order. This difference in the two pictures is pretty amazing. Is there any reason you did not shoot the E-PL5 in RAW? Also, did you set the ISO to 2500 or was that automatically set by the camera?

Lightroom can't import EPL5 Raws yet and I don't like the Olympus editor much.
I did the first as a RAW because that was my habit with the EPL1. This is possibly a skew in the test (I'd certainly feel a dolt (this could be the case!) if all those EPL1 photos I did could have been much better just using Jpegs). The results above echo another comparison I was able to do (using ideal on a tripod settings for both photos) - but I haven't shown that for privacy considerations.
I've set the upper limit on the EPL5 to 3200 and it was set to auto ISO, so yes it did choose 2500 itself. I've been very impressed with ISO 3200 in my flat.

Edit - sorry, I first showed a data reduced example of the EPL1 shot - it is now the full thing.

Have you tried seeing if there is an update to Lightroom? I had a trial of Lightroom 4 and it did open the files.

There is also a RAW to DNG converter from adobe that is free. it will go in and convert the new raw formats to DNG so older versions can work with them. It takes a while for it to run though a thousand images which sucks, but then you should be able to use your favorite raw editor.

My Lightroom 4.2 won't import EPL5 Raws and it says there are no updates available.
Could you be mixing the EPL5 and EM5 up?

From your house photos I'd say the IBIS works splendidly on your long zoom lens!

Although using an e-pL1 I'm sure ;
Regardless of RAW or Jpeg your e-pL1 example is truly awful.

I recently took side-by-side photos with the same 17mm lens on my e-P1 & an e-pM5 and the detail differences were subtle, mostly sharpness and detail : the e-P1 is at the lowest end of Olympus' sharpness scale anyway.

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Oly e-P1&17mmF2.8 e-600, e-410&40-150MkI, E-1&14-54MkI, Tokyo-Koki 300mm
Lumix G1&Yashinon45F1.7, e-pL1&CZJ135F3.5, e-P2&45mm. e-pL2&30mmF2.8

I may not have been trying as hard to be steady as normal on it. I took the shot for someone to compare focal lengths. It may indeed be substandard and this one swallow may not make a Spring.
The images are significantly cropped. The building is about 270 metres away. You can least judge the EPL5 one on its own terms - for something 270 metres away at ISO 2500 it think it is doing quite well.
This is the photo view I took the crops from (this is data reduced from the EPL1):

I think the IQ results of the EPL5 must be almost the same if not identical to the EM5. However - it is making a presumption to think it will be identical.

Have you gotten around to testing the video yet? One major thing that kept me from keeping the older Pen cameras was the serious image wobbling that occurred with the camera's digital stabilizer. The video was essentially useless unless if IBIS was turned off. If the E-PL5 actually uses the sensor to stabilize video like the E-M5, then I may give this camera a serious look for the lower form-factor.

The weather on Saturday is predicted to be sunny. I'll do a good bout of shooting then. I'll add video the the itinerary (I haven't actually tried it yet!).

I'd like to see jpeg photos taken with each camera on a tripod or other stable support at the same time and place and camera settings. I doubt the E-PL5's shot will look noticably brighter, sharper or more detailed than the E-PL1 based on my experiences with the E-PL1 and E-M5.

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E-PL1, E-M5, 14-42, 40-150